The most senior judges in England and Wales have warned the Justice Secretary that proposed increases in court fees are at risk of causing "irremediable damage to the system of civil justice as a whole".

Claims by Ministry of Justice (MoJ) officials that the number of cases being brought to court will not change in response to planned fee rises appear t o "contradict a basic law of economics", the Senior Judiciary, which includes the Lord Chief Justice, Lord Thomas, said.

In response to a consultation, the judges said research by the Government department into the impact of the reforms on access to justice was "clearly inadequate" and in the face of a lack of evidence it must be presumed the number of cases will go down.

"It is of the utmost importance that short term proposals to save costs do not lead to a vicious circle of decreased volume and increased costs and result in irremediable damage to the system of civil justice as a whole," they said.

Under its proposals, the Government wants to i ncrease court fees with a view to reducing the deficit on the costs of the civil and family courts and in a significant number of cases charge at a level above the cost of the proceedings in question.

"The Judiciary has for many years consistently made clear that it does not support the policy of successive Governments that the justice system should be self- financing," the judge said. "That is an issue of principle which must be the subject of debate and ultimate decision by Parliament."

The Senior Judiciary response went on: "Quite apart from these matters, it is difficult to see the merit of proposals which would increase the cost to litigants but provide no tangible benefit to them or the judicial system more generally, through the hypothecation of the increased fees."

Looking at research undertaken by the MoJ, the judges said it had so far been "clearly inadequate" in assessing the consequences of the proposals on the ability of parties to afford access to courts and on their willingness to do so.

The Senior Judiciary said the MoJ " accepts that the research has been very limited" and highlights that the work has been undertaken by consultants who are closely involved in the development of the fee proposals on behalf on the Government department.

In addition, the research consisted of 18 telephone interviews including 12 large organisations, debt recovery agencies and solicitors concerned with debt recovery claims.

A further two were solicitors who make personal injury claims on behalf of clients and the remaining four were solicitors who represent privately paying private law family clients.

The judges add the department "provides no evidence on the likely effect on individuals and small and medium-sized businesses".

Looking at one of the proposals more closely, which would charge fees for certain cases at a level above the cost of the proceedings in question, the Senior Judiciary said: " There is no evidence advanced for the apparent assumption that the size of a claim and the means of the party making it, are necessarily related."

They added: "The research so far conducted has not investigated the likely impact of the proposals on this broad range of businesses and individuals drawn from all sections of society.

"Nor has it investigated the broader social implications the proposals may have, since it cannot be doubted that access to justice at reasonable cost plays a vital role in moderating individual and commercial behaviour more generally, and is therefore of benefit to all, whether they are ' court users' or not."

Claims that the number of cases are unlikely to change appear to "contradict a basic law of economics concerning the elasticity of demand", the judges said.

The judges said they were concerned that a number of issues of policy - for Parliament to decide - should be openly acknowledged and explained so there can be a fully informed debate.

They said: "Is it right that parties in civil proceedings, many of whom will not have money to spare, should subsidise proceedings between divorcing couples, still less proceedings for the protection of children?"

"If, as all agree, it is essential in the public interest to provide a family justice system, and it cannot be fully self-financing, should the cost be found from society at large or from a charge, essentially by way of taxation, on those who need to bring claims in the civil courts?"

Courts minister Shailesh Vara said: " We have the best court system in the world and we must make sure it is properly funded so we keep it that way.

"Hardworking taxpayers should not have to subsidise millionaires embroiled in long cases fighting over vast amounts of money, and we are redressing that balance.

"Vulnerable groups must also be protected, which is why we are keeping fees the same for sensitive family issues, including adoption applications and child contact.

"Moreover, we are scrapping the application fee for victims of domestic violence seeking injunctions to protect themselves.

"We have consulted on proposals and are now considering the responses. We will set out our next steps in the next few weeks."